The invention relates generally to testing the output of video display generators and, in particular, to a dynamic video test for the single or multiple channel video output of a color or monochromatic-type video display generator.
Video display generators are used to output on one or more channels analog video signals created from digital raster data. These analog video signals create color or monochromatic ("mono") video images. A mono image is generally created from a mono signal on a single video channel, while a color image is generally created from several distinct color signals, each on a separate video channel. For example, a standard red, green and blue (RGB) color image is created from a red, a green and a blue analog video signal, each being output from a video display generator on a distinct output channel. The video display generator may also output an overlay image (which "overlays" the video image) on a separate video channel. Within each channel, a mono or color output video signal may have several distinct components, including an "active video" portion, a "video blank" portion and a "video sync" portion, all of which are well known in the art and are not described in detail herein.
To create an analog video signal from digital raster data, a video display generator must retrieve the digital data from memory to create a digital signal. The display generator then creates an analog signal from the digital signal with a digital-to-analog (D/A) converter. The analog signal is then amplified and displayed as a video image.
During the video image creation process, many factors adversely affect the analog video signal output from the display generator. For example, signal interpolation within the D/A converter introduces distortions to the analog signal. These distortions are then magnified during amplification of the signal. In addition, the analog amplifier, which functions differently at different signal frequencies, creates further distortion in the analog output. Because of the non-linearities introduced by the elements of the video display generator, the output analog signal is not a completely accurate representation of the digital data from which it was created. Although perfectly accurate video images cannot be expected, it is often necessary to ensure that the displayed image is as accurate a representation of the digital data as possible.